diff --git a/src/Two/SlackProvider.php b/src/Two/SlackProvider.php
index 299f794c..225ff023 100644
--- a/src/Two/SlackProvider.php
+++ b/src/Two/SlackProvider.php
@@ -5,7 +5,7 @@
 use GuzzleHttp\RequestOptions;
 use Illuminate\Support\Arr;
 
-class SlackProvider extends AbstractProvider
+class SlackProvider extends AbstractProvider implements ProviderInterface
 {
     /**
      * The scopes being requested.
diff --git a/src/Two/TwitterProvider.php b/src/Two/TwitterProvider.php
index dd1f54be..b6661f71 100644
--- a/src/Two/TwitterProvider.php
+++ b/src/Two/TwitterProvider.php
@@ -5,7 +5,7 @@
 use GuzzleHttp\RequestOptions;
 use Illuminate\Support\Arr;
 
-class TwitterProvider extends AbstractProvider
+class TwitterProvider extends AbstractProvider implements ProviderInterface
 {
     /**
      * The scopes being requested.